Field of the Invention
This invention relates generally to the treatment of vegetable sources of nutrients, and more particularly to the treatment of vegetable proteins and carbohydrates in order to improve the palatability and digestibility thereof, to an extent that permits such foodstuffs to be utilized as nutrients for human and animal consumption.
The latent nutritional values present in many vegetables, particularly the oilseed vegetables such as soybeans and other legumes and cottonseeds, is well known. Utilization of these nutrient sources has been severely hampered by the presence in these vegetable nutrients of naturally occurring substances that interfere with their digestibility and palatability.
A particular field of use where it would be desirable to utilize vegetable nutrients is in the preparation of milk substitutes for the replacement of mothers' milk, particularly in the feeding of young farm animals such as calves and pigs. Milk replacers for these young animals has become an important sector of the animal feed business. Understandably, dried milk products such as skim milk, whey and casein have been considered to be the most desirable nutrient source for milk replacers. However, the unpredictable and relatively high price of milk derived nutritive source has stimulated a interest in lower cost alternative nutrient sources provided that they are capable of producing equivalent growth rates to that produced by milk derived substitutes in the young animals to which they are fed.
The principal deficiencies of vegetable nutrient sources is their typical beany flavor and their poor digestibility. The beany flavor, particularly when used as an animal feed can be overcome by cooking or toasting. However, the poor digestibility of vegetable nutrients, such as soy protein is caused by the presence of oligosaccharide sugars, antinutritional factors as trypsin inhibitor and proteins that show antigenicity.
These sugars are antinutritional factors, because they cause flatulence. This flatulence results in discomfort, diarrhea, loss of appetite and poor growth, all of which has prevented the wide-scale use of vegetable nutrients as milk replacers for human consumption.
The proteins with antigenicity are believed to interfere with or slow down the growth rate of young animals. The antigenic factors are generally associated with the presence of glycinin, betaconglycinin, lectin and urease that occur naturally in vegetable nutrients such as soy beans and cottonseed. In young animals, the presence of these substances results in diarrhea, poor growth and even mortality.
Vegetable nutrients especially soy products also typically contain factors which inhibit the natural digestive action of the trypsin enzyme in the intestine. These trypsin inhibiting factors may be reduced to below 1.0 mg inhibited trypsin per gram product by heat treatment, for example by heating to a temperature above 85.degree. C. for 6 minutes.
The deficiencies of vegetable nutrient are well known and many attempts have been made to provide treatment processes to improve their palatability and digestibility. U.S. Pat. No. 4,512,973 discloses inactivation of soybean trypsin inhibitors with a trypsin enzyme derived from starfish in combination with a supplementary proteolytic enzyme.
Several methods for hydrolyzing the flatulence producing sugars have also been suggested. The flatulence producing sugars are those sugars, principally the alpha oligosaccharide, stachyose, raffinose and saccharose, that are not digested in the digestive tract and enter the lower intestine intact where they are anaerobically fermented which results in the production of carbon dioxide, hydrogen and methane. U.S. Pat. Nos. 4,483,874, 4,376,127, 4,216,235 and 3,632,346 describe various enzymatic treatments which are indicated to result in hydrolysis or degradation of the flatulence producing sugars to digestible mono- and di-saccharide sugars.
U.S. Pat. No. 4,485,874 discloses the preparation of a milk substitute from crude vegetable protein and carbohydrate sources using an enzyme having multiple carbohydrase activities. The addition of other enzymes such as amylases and/or proteases to the carbohydrase enzyme is suggested.
In the treatment process described in U.S. Pat. No. 4,483874, a crude source of vegetable protein and carbohydrate, for example, full fat or defatted beans or cottonseed, soy flour or meal, is cooked to inactivate trypsin inhibiting factors. The cooked material is slurried in water and contacted with the enzyme at an elevated temperature that is below that at which the enzyme is inactivated, at or slightly below 50.degree. C., the resulting product may be fed directly as a substitute milk source or may be augmented with additional sources of fat, protein and carbohydrate depending on the nutrient content of the starting raw material. Typically, augmentation is required to obtain the nutrient level of mother's milk.
It has been determined that although, the end products obtained by the process of U.S. Pat. No. 4,483,874 are satisfactory fluid milk substitutes, the disclosed process is not susceptible to scale up for commercial production, particularly where it is desirable, or it typically is where an animal milk replacer is the desired end product, to provide a dried product which is purchased and reconstituted by the end user.
Vegetable nutrient sources, for example, soybean meal or flour, form highly rigid slurries when mixed with water which are difficult to handle on a commercial scale.
Accordingly, it is necessary to utilize highly dilute slurries having relatively low solids content, generally below 15 percent by weight and typically below 10 percent by weight in order to permit handling of the slurry without the necessity of special pumps, increased electrical costs, etc. Typically, soybean flour slurries having 20 percent by weight solids content show a viscosity increase during storage from about 2,000 to about 7,000 cps at 40.degree. C.
Low solids content slurries, while desirable from the standpoint of handleability during processing, are cost inefficient when a dried product is desired. For example, the cost of spray drying a 10 percent solids slurry obtained from the procedure of the '874 Patent may be as much as 3.9 times the cost of spray drying a 30 percent solids slurry per unit weight of product.
Thus, it is highly desirable to develop an efficient and effective process for treating vegetable protein and carbohydrates in order to improve palatability and digestion for animal and human consumption. Additionally, it is also highly desirable to develop a milk substitute which is cost efficient and easy to use.